MarLIN Glossary

S

Sacoglossan
Member of the Order Sacoglossa: shelled and slug-like opisthobranchs with a radula bearing a single row of teeth adapted for suctorial feeding on algae (Ruppert & Barnes, 1996).

Salinity
A measure of the concentration of dissolved salts in seawater. Salinity is defined as the ratio of the mass of dissolved material in sea water to the mass of sea water (UNESCO, 1985). But this 'absolute' definition is not practical. Salinity was measured by a chlorinity titration but with the development of the salinometer, which utilizes conductivity, a new definition was developed. The 'practical salinity' (S) of a sea water sample is defined as the ratio of the electrical conductivity of the sample (at 15 °C, and one standard atmospheric pressure) to that of a standard solution of potassium Chloride (KCl). A ratio of 1 is equivalent to a 'practical salinity' of 35 (UNESCO, 1985). Until recently, salinity was expressed as parts per thousand (ppt or ). Subsequently, adoption of the 'practical salinity' gave rise to the 'practical salinity unit' (psu). However 'salinity', defined as the ratio of two quantities of the same unit, is a 'dimensionless quality', i.e. takes no units. Therefore, it is correct to speak of a salinity of 35 (UNESCO, 1985). Baretta-Bekker et al. (1992) suggested that, in most cases, where a high degree of accuracy is not required, old and new figures for salinity can be used interchangeably. However for the sake of accuracy, when referring to salinity in our on-line reviews, the units used by the original authors are quoted in the text. Freshwater is regarded as < 0.5  (limnetic), seawater as > 30  (euhaline), and brackish water as intermediate, including oligohaline, mesohaline and polyhaline waters (based on McLusky, 1993).

Saltmarsh
Areas of alluvial or peat deposits, colonized by herbaceous and small shrubby terrestrial vascular plants, almost permanently wet and frequently inundated with saline waters (from Long & Mason, 1983).

Sampling
The selection of a set of data, or the collection of a quantity of material, or of a set of individuals from a population with the purpose of measuring a given characteristic of that sample (based on Dooley & Kirkpatrick, 1993).

Sand Bank
Sand which rises from a level seabed towards the surface, often levelling-off in shallower depths. As defined for the EC Habitats Directive, 'sandbanks which are slightly covered by seawater all the time' are: "Sublittoral sandbanks, permanently submerged. Water depth is seldom more than 20 m below Chart Datum". They can be non-vegetated or vegetated and can include free-living species of the Corallinacea family. (European Commission 1995.)

Sea Anemone
A type of cnidarian (Order Actiniaria, Phylum Cnidaria) with a large solitary polyp, consisting of a base, a column, and a ring of tentacles around a central mouth. So called due to their resemblance to flowers.

Sea Cucumber
A common name for members of the Class Holothuroidea (Phylum Echinodermata), which refers to a group of 'cucumber' shaped marine organisms closely related to starfish and sea urchins.

Sea Loch
In Scotland - a marineinlet (q.v.) which has fjordic or fjardic features, entered by the tide (on each cycle), and with a salinity generally greater than 30 ‰. Brackish conditions may be periodically established, particularly in the surface layers (based on Earll & Pagett, 1984). As defined for the EC Habitats Directive, 'open sea lochs' are "simple glacial features which are longer than they are wide, have no entrance sill and in which the seabed slopes gradually towards the head". See also 'fjard', 'fjord'.

Sea Urchin
Common name for members of the Class Echinoidea (Phylum Echinodermata), characterized by a rigid test or shell, usually spherical or ovoid but occasionally flattened, and covered by mobile spines of varying length. Cf. urchin.

Seabed
The sea floor.

Seagrass
A flowering plant (PhylumAngiospermophyta) that is adapted to living fully submerged and rooted in estuarine and marine environments. Although not true grasses, all seagrasses are monocotyledons. The group is defined by their ecology rather than their phylogeny. In British waters, seagrasses are represented by the genus Zostera (eelgrass). Several members of the genus Ruppia (tasselweeds) also occur in marine and estuarine environments. Ruppia may be considered a seagrass, although this is not accepted universally (Green & Short, 2003).

Segment1) A semi-independent, serially repeated unit of the body (Barnes et al., 1993). 2) In Arthropods - one of a series of units of an appendage. Also segments of the body (also referred to as somites) (based on Stachowitsch, 1992).

Sensitivity
(conservationassessment) An assessment of the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor.

Seston
The total suspended particulate matter in the water column (Lincoln et al., 1998), including plankton, nekton and both organic and inorganic suspended particulates.

Sheltered
Of wave exposure - coasts with a restricted fetch and/or open water window. Coasts can face prevailing winds but with a short fetch (< 20 km) or extensive shallow area offshore, or may face away from prevailing winds (from Hiscock, 1990).

Shingle
Beach pebbles (q.v.), normally well-rounded as a result of abrasion. In relation to coastal vegetated shingle structures, 'shingle' is considered as any sediment which has a grain size of between 2 and 200 mm (Sneddon & Randall, 1993).

Shore Platform
A surface eroded by wave action, forming a flat rock platform in the intertidal zone (based on Ritchie, Smith & Rose 1978.) The more correct term for 'wave-cut platform' or 'abrasion platform'.

Sill
Lowest point on a submarine ridge or saddle at a relatively shallow depth, separating a basin from an adjacent sea or another basin (from Baretta-Bekker, Duursma & Kuipers, 1992). In sea lochs, sills are structures commonly formed by glaciation, found at the mouth or elsewhere along the length of the loch. Such a threshold can limit water exchange.

Siphon
Any extension of the mantle margin associated with incurrent or excurrent respiratory streams (Graham, 1988). In gastropods the inhalent siphon is often supported by an extension of the shell, the siphonal canal.

Siphonoglyph
A flagellated groove extending from the mouth to gastrovascular cavity providing an incurrent of water into the gastrovascular cavity of anemones and corals (adapted from Stachowitsch, 1992).

Siphonozooids
Small inhalent polyps in polymorphic octocoral colonies that drive water into the colony. The polyp has reduced tentacles or is tentacle-less and possesses a well-developed siphonoglyph (see above) (adapted from Stachowitsch, 1992).

Site Of Special Scientific Interest
An area of land or water notified by the Nature Conservancy Council or its successor agencies under the Wildlife and Countryside Act 1981 as being of special nature (can include geological) conservationimportance.

Skerry
Low-lying rocky island or reef, often without terrestrial vegetation, and frequently swept by the sea (based on Scott & Palmer 1987).

Slack Water
Period in a tidal cycle usually between flood- and ebb-tide, when the strength of tidal streams is near zero.

Slate
A rock particle which is flattened and thin and corresponds to the diameter of a cobble (64-256 mm) (based on Hiscock, 1990). Also describes the type of rock which constitutes such loose-lying substrata.

Soft Coral
The common name for the Order Alcyonacea (Phylum Cnidaria), a group of solid fleshy bodied corals in which the thick body tissue (coenenchyme) is strengthened with calcareousspicules (adapted from Hayward et al., 1996).

Special Area Of Conservation
A site of [European] Community importance designated by the [EU] Member States through a statutory, administrative and/or contractual act where the necessary conservation measures are applied for the maintenance or restoration, at a favourable conservation status, of the natural habitats and/or the populations of the species for which the site is designated (Commission of the European Communities 1992). (This status is achieved by sites adopted by the European Commission).

Special Protection Area
A site of European Community importance designated under the Wild Birds Directive (Commission of the European Communities Council Directive 79/409/EEC of 2 April 1979 on the Conservation of Wild Birds).

Spermatophore
A packet of sperm, produced by some species of animals (Abercrombie et al., 1973). In decapod crustaceans, the packet of sperm is formed in the vas deferens of the male, and is transferred to the female with the aid of modified first pair of pleopods (adapted from Stachowitsch, 1992).

Spicule
Variously shaped or sized calcareous or siliaceous skeletal elements used in the endoskeleton of sponges and echinoderms (Stachowitsch, 1992). May be highly variable in shape, especially in holothurian echinoderms forming anchors, anchor plates, baskets, buttons and wheels. May also be termed 'deposits' in echinoderms.

Stenophagous
Utilizing, or tolerant of, only a limited variety of food or food species (Lincoln et al., 1998).

Stenothermal
Tolerance of a narrow range of temperatures.

Stochastic
Of a random variable - having a probability of distribution, usually with finite variance.

Strait
Any deep (> 5 m) tidal channel between two bodies of open coastal water. Strictly, a strait is the stretch of water between an island and its mainland (or adjacent islands) (from Earll & Pagett, 1984.)

Strandline
A line on the shore comprising debris deposited by a receding tide; commonly used to denote the line of debris at the level of Extreme High Water (from Lincoln & Boxshall 1987).

Strategic Environmental Assessment
The formalised, systematic and comprehensive process of evaluating the environmental impacts of a policy, plan or programme and its alternatives, including the preparation of a report on the evaluation and the use of the findings in publicly-accountable decision-making (Pritchard 1993) (cf. 'Environmental Assessment').

Stratum
In ecology - a horizontal layer of vegetation within a stratified plant community (from Lincoln & Boxshall, 1987).

Stress
"A chemical or physical process that leads to a response within an organism, or at the levels of whole organisms or assemblages" (from Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection - GESAMP, 1995).

Subchela
Appendage where the terminal segment (dactyl) folds against the blunt end of the subterminal segment (propodus), which lacks the immovable finger of a chela (see above) (Ruppert & Barnes, 1996). [subchela&topic=Species">View image]

Sublittoral
The zone exposed to air only at its upper limit by the lowest spring tides, although almost continuous wave action on extremely exposed coasts may extend the upper limit high into the intertidal region. The sublittoral extends from the upper limit of the large kelps and includes, for practical purposes in nearshore areas, all depths below the littoral. Various subzones are recognised (based on Hiscock, 1985.) (Cf. 'subtidal').

Sublittoral Fringe
The upper part of the sublittoral zone which is uncovered by the tide. On hard substrata, the zone is characterized by the kelpsLaminaria digitata and Alaria esculenta. The lower limit of this zone is marked by the upper limit of the truly sublittoralkelpLaminaria hyperborea. This species assemblage does not occur on all British coasts (based on Lewis, 1964).

Surge Gully
A narrow marineinlet on a small scale, usually formed by erosion of a rocky shoreline on exposed coasts. Their aspect, facing into waves, and their funnel effect, means that waves entering them become higher and of shorter wavelength, causing back-and-forth or multi-directional water movements of considerable force.

Surrogate Species
Species which are likely to change if the whole community is changing and therefore respond to change on behalf of the community.

Surveillance
A procedure by which a series of surveys is conducted in a sufficiently rigorous manner for changes in the attributes of a site (or species) to be detected over a period of time. Surveillance is often conducted to identify normal background variation ('noise') in order that abnormal changes can be identified by a monitoring programme. (From Marine Conservation Monitoring Workshop, January 1993.) The term is also applied to compliance surveillance to ensure that agreed or required measures are followed. (See also 'survey'. Cf. 'monitoring').

Survey
An inventory of the attributes of a site, area or region in terms of habitat and associated organisms (or of the distribution and/or autecological characteristics of selected species), usually by means of a standardised procedure (based on Marine Conservation Monitoring Workshop, January, 1993).

Sustainability
Maintaining the environment's natural qualities and characteristics and its capacity to fulfil its full range of functions, including maintenance of biodiversity (from English Nature, Planning for environmental sustainability, June 1994).

Sustainable Development
"Development that meets the needs of the present without compromising the ability of future generations to meet their own needs" (World Commission on Environment and Development, 1987 (the 'Brundtland' Report)).

Swell
Sea waves that have left the area where they were generated by the wind, or that have remained after the generating wind has disappeared (from Baretta-Bekker, Duursma & Kuipers 1992.)

Cooke, A. & McMath, M., 2000. SENSMAP: Development of a protocol for assessing and mapping the sensitivity of marine species and benthos to maritime activities. Countryside Council for Wales, Bangor, CCW Marine Report: 98/6/1, (2000, Working draft).

Cornelius, P.F.S., 1995. North-West European Thecate Hydroids and their Medusae. Part 2. Sertulariidae to Campanulariidae. Synopses of the British Fauna (New Series) (ed. R.S.K. Barnes & J.H. Crothers), The Linnean Society of London. Shrewsbury: Field Studies Council.[Synopses of the British Fauna no. 50]

GESAMP, 1995. Biological indicators and their use in the measurement of the condition of the marine environment. (IMO/FAO/UNESCO/WMO/WHO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection, GESAMP Reports and Studies No. 55.

Glémarec, M., 1973. The benthic communities of the European North Atlantic continental shelf. Oceanography and Marine Biology: an Annual Review, 11, 263-289.

Mills, E.L., 1969. The community concept in marine zoology, with comments on continua and instability in some marine communities: a review. Journal of the Fisheries Research Board of Canada, 26, 1415-1428.

Ratcliffe, D.A. (ed.), 1977. A nature conservation review. The selection of biological sites of national importance to nature conservation in Britain. Cambridge: Cambridge University Press for Nature Conservancy Council and the Natural Environment Research Council.

Woodward, H.B., 1912. The geology of soils and substrata, with special reference to agriculture, estates, and sanitation London: Edward Arnold

World Commission on Environment and Development. 1987. Our common future: the report of the World Commission on Environment and Development (the ‘Brundtland Commission’). Oxford: Oxford University Press.